ORIGINAL ARTICLE Effect of process parameters on the cutting quality in lasox cutting of mild steel M. Sundar & A. K. Nath & D. K. Bandyopadhyay & S. P. Chaudhuri & P. K. Dey & D. Misra Received: 31 May 2007 / Accepted: 18 January 2008 / Published online: 14 February 2008 # Springer-Verlag London Limited 2008 Abstract Samples of mild steel have been cut on a CO 2 laser machine using the principle of laser assisted oxygen cutting (LASOX). The combined effects of input process parameters (cutting speed, gas pressure, laser power and stand off distance) on cut quality (heat affected zone (HAZ) width, kerf width and surface roughness) have been studied. Regression analysis has been used to develop models that describe the effect of the independent process parameters on cut quality. Using the developed model, we attempted to optimize the input parameters that would improve the cut quality (minimization of HAZ width, kerf width and surface roughness), increase the productivity and minimize the total operation cost. We found from the study that the gas pressure and cutting speed had pronounced effect on cut quality. Low gas pressure produces lower HAZ width, lower kerf width and good surface finish whereas increase in speed results in higher HAZ width, lower kerf width and good surface finish. Keywords HAZ . Kerf width . Laser cutting . Surface roughness . Thick steel cutting 1 Introduction Lasox cutting is achieved by a combination of laser power and the power produced by the exothermic reaction of iron and oxygen. This exothermic reaction produces vast amounts of power which helps in carrying out the cutting process. In the traditional laser cutting process, the exothermic reaction [1, 2] contributes only around 25% of the total cutting power. In lasox cutting process the power produced by the exothermic reaction is increased to around 80% and the laser power is used only to facilitate this exothermic reaction. This produces a vast amount of energy, which can be used for cutting of thick carbon steel greater than 50 mm [3] thickness. A special nozzle is used which is capable of operating at high stagnation pressure, high exit mass flow rate and high exit velocity. The important factor is to make sure that all the oxygen react with Fe to produce power. This is achieved by having the diameter of the laser foot print higher than the diameter [3] of the gas jet. To achieve this nozzle assembly with a short focal length lens is used. The focal point is kept inside the nozzle assembly and the diverging beam is used for heating the metal surface. Figure 1 shows the schematic arrangement of laser assisted oxygen cutting process. Of particular interest to manufacturers using lasox cutting are the maximization of the productivity and the obtainment of subsequent quality of components made by the lasox cutting process. Both these aspects are governed by the selection of appropriate process parameters, which are unique for each material and thickness. The combina- tion of the cutting speed, gas pressure, laser power and stand off distance is of paramount interest for obtaining good cut quality. In fact the lasox cutting input parameters determine the quality of cut. These parameters are usually Int J Adv Manuf Technol (2009) 40:865–874 DOI 10.1007/s00170-008-1413-9 DO01413; No of Pages M. Sundar (*) : D. K. Bandyopadhyay : S. P. Chaudhuri : P. K. Dey : D. Misra School of Laser Science and Engineering, USIC Building, Jadavpur University, Calcutta 700032, India e-mail: marimuthusundar@gmail.com A. K. Nath ICL, RRCAT, Indore, India